1. Field of the Invention
Embodiments of the invention relate to a liner flotation system.
2. Description of the Related Art
It is often desirable in the oilfield industry to drill horizontal wells to produce oil and gas. These horizontal wells may be either cased holes or open holes. Longer horizontal well sections maximize oil and gas recovery and are thus in longer lengths.
However, these “extended reach” horizontal wells have become so long that it is difficult to get a liner to depth when both the liner and the well are full of fluid. In particular, the weight of the work string must be sufficient to provide a downward force that overcomes the frictional/drag force produced by the liner rubbing against the bottom of the horizontal well. When the conditions of the horizontal section of the well become severe enough to create a frictional force that cannot be overcome by the work string weight, the liner cannot be advanced any further into the well. This limitation hinders maximum recovery from oil and gas formations.
Recently, operators have preferred a “wet shoe” at the end of the liner. A wet shoe occurs when cement does not set around or obstruct a float valve (e.g. a check valve) at the end of the liner so that fluid flow remains established through the liner and float valve into the well. A wet shoe enables operators to conduct subsequent operations after cementing of the liner, such as pumping plugs or perforating guns to the toe of the well.
Therefore, there is a need for new and improved systems for running liners into horizontal wells and conducting subsequent well operations.